1. Field of Invention
The present invention relates to a package structure and the manufacturing method thereof. More particularly, the present invention relates to a stacked chip package structure and the manufacturing method thereof.
2. Description of Related Art
Following the quick progress in the fabrication of integrated circuits, the design of the electrical products becomes more complex and high-speed and multi-function chips are developed. As the integration of ICs keeps increasing and the layout of the high-speed semiconductor devices becomes dense, more heat is generated by the semiconductor device per unit area in a certain period. Thus, it is important for the design of semiconductor devices to consider the heat dissipation issue, in order to prevent damages to the electronic devices or the chips.
Conventionally, a metal heat dissipation plate, for dissipating heat resulting from the operation of the chip, is disposed on the outer surface of the mold compound, so that the heat dissipation plate can help dissipate heat generated from the operation of the chip into the external environment outside the mold compound.
FIG. 1 is a cross-sectional view of a prior quad flat no-lead (QFN) package structure. Referring to FIG. 1, the QFN package structure 100 includes a leadframe 110, a chip (or die) 120, a plurality of wires 130, a heat sink 140 and a mold compound 150. The leadframe 110 includes a die pad 112 and a plurality of leads 114. The chip 120 has an active surface 120a with a plurality of bonding pads 122 disposed on the active surface 120a, while the chip 120 is fixed to the die pad 112. Each bonding pad 122 is electrically connected to one of the leads 114 through the wire 160 by wire bonding.
As shown in FIG. 1, the heat sink 140 is disposed on the mold compound 150. The shape of the heat sink can be varied depending on the requirements of heat dissipation and layout design. The mold compound 150 is filled within the space between the heat sink 140 and the leadframe 110, covering the leads 114, the bonding pads 122 and the wires 130. As the chip 120 is in operation, the produced heat can be dissipated by the heat sink 140 through the mold compound 150.
For electronic modules (such as DRAMs) with multiple chip packages, the chip packages are usually stacked up and connected in parallel to provide better electrical properties and faster transmission speed. Hence, the size and the area of the package structure are reduced. Although the heat sink may assist heat dissipation, multiple wires are needed to connect the chip package structures for the stack type package structure. Therefore, the costs, the complexity and the uncertainty of the fabrication processes are increased.